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I guess, it's rather a problem with AS related pin options.
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You were right. The operation of programming EPCS4 was not sometimes successful with "Enable INIT_DONE output" and "Enable device-wide output enable (DEV_OE)" options checked. So I have been testing other options. I have switched the option "Reserve all unused pins: As output driving ground" to "As input tri-stated" and my design is 100% stable and functional now. Operations of programming, verifing or erasing EPCS4 are always OK.
"Enable INIT_DONE output" and "Enable device-wide output enable (DEV_OE)" options are not necessary.
Thank FvM for your help!
Honored Contributor
